The scrap briquetting machine is used to extrude various loose-density ferrous or non-ferrous metal blocks, cutting curls, scraps, etc. into the dense-density cakes under the action of the hydraulic punch so as to facilitate transportation and storage. Finally, these scrap cakes are put into the metal smelting furnace and recycled after smelting. The Chinese Patents “CN201010156906.4—Horizontal Scrap Cake Machine” and “CN 201010277629.2—Scrap Metal Briquetting Machine” applied for by the applicant discloses their structures and operating principles: the transverse feeding primary pre-pressing, longitudinal secondary pre-pressing and vertical final pressing of scraps realize the three-way extrusion of metal scraps; due to the reasonable compression mode and large compressive force, the very large compression ratio and high compression efficiency can be achieved.
In practice, the composition of the materials to be processed is complicated. For the carbon-containing ferrous metals (such as carbon steel, etc.), they are relatively hard and brittle. For the existing briquetting machine, a relatively close fit is generally designed at the junction among the pre-extruding cavity, secondary extruding cavity and final pressing cavity and between the punch and cavity wall. This type of small gaps can be taken as the shearing surface during the feeding of the extruding punch so as to shear off relatively brittle ferrous metal curls, shavings, etc. But in the recycling technology of electric wires, cables and other wire materials, granular copper particles can be obtained, which are visually called “copper rice” in engineering. This type of granular metal materials has very high density, and copper itself is very soft. At the junction among the small gaps, when all extruding punches move forwards or return to the original position, the residual materials during each time of feeding often receive the complex extrusion force in many directions so as to very easily and directly form the dense copper cakes under the conditions of temperature and pressure. During the feeding of the extruding punch in the next step, the extruding punch no longer feeds the materials by pushing but shears or rolls the materials into copper cakes, which cause the sharp increase of the extrusion force in various directions. In practical production, some virtual travels generally need to be carried out after several times of extrusion so as to process the internal blockage. These extra processing procedures not only greatly reduce the work efficiency but also affect the continuity of operation. During the serious soft metal blockage, the equipment may be damaged, the “cylinder burst” accident may occur, and serious potential safety hazards may occur.